For the control of the temperature of flowing media a solution is known according to which the temperature of the medium discharging from a heating device is measured and the heating of the heating device is controlled by a feedback control circuit so that the medium discharging from the heating device is of a prescribed temperature. With this solution, the control circuit follows relatively slowly the changes in the flow rate or in the temperature of the medium entering the heating device. Consequently, this control is not quick enough especially if the temperature of a smaller quantity of medium has to be controlled.
In another known solution, the flowing medium is led through a heating device of high heat capacity, set to the prescribed temperature. This solution is used e. g. in case of introducing a physiological fluid into a human organism where the safety requirements do not permit that the heating device is of a higher temperature than the prescribed temperature of the fluid. In a known method, the physiological fluid to be introduced is conducted through a spiral hose arranged in a thermostatic water bath.
EP-A-No. 112-104 relates to an apparatus for peritoneal dialysis where the dialysing fluid is pumped through a flat bag arranged between two heating plates of high heat capacity into a gravity tank and conducted therefrom through the same bag by gravity into the peritoneal cavity of the patient. The heating plates are maintained continuously at body temperature. This temperature control is based also on the fact that the medium flowing slowly enough through a heating device of high heat capacity will achieve the prescribed temperature at the outlet. This control method can be applied only in the case of small flow rates, it does not take into consideration the changes of temperature of the entering fluid, requires a relatively voluminous heating device of high energy consumption and is less applicable due to its time-lag for a follow-up control of the temperature.